Swedish authorities have dropped an investigation into allegations of rape against WikiLeaks co-founder Julian Assange.

Prosecutors decided that, after so many years waiting for the case to progress, the Swedish woman who leveled the rape accusation against Mr Assange had a faded memory of what happened on the night in question.

Assange has always maintained his innocence.

While the victim’s statements about the events, alleged to have taken place in 2010, were deemed “coherent, extensive and detailed”, Sweden’s deputy director of public prosecution Eva-Marie Persson said the evidence had since “weakened considerably”.  

WikiLeaks founder Julian Assange arrives at court in London on May 1, 2019 to be sentenced for bail violation. Photo: AAP

It was “to such an extent that there is no longer any reason to continue the investigation”, Ms Persson announced on Wednesday morning (Australian time).

Assange, who is facing the threat of extradition from Britain to the US on espionage charges, is in Belmarsh Prison in Britain.

There, he has been serving a 50-week sentence for jumping bail in 2012 and fleeing to the Ecuadorian embassy in London on an arrest warrant stemming from the alleged sex crimes. 

• Related: Pamela Anderson cancels Assange visit

British lawyers have reportedly been unable to contact the 48-year-old to inform him that the rape investigation has been “discontinued”.

Kristinn Hrafnsson, WikiLeaks editor-in-chief, said, “Sweden has dropped its preliminary investigation into Mr Assange for the third time, after reopening it without any new evidence or information.

“Let us now focus on the threat Mr Assange has been warning about for years: the belligerent prosecution of the United States and the threat it poses to the First Amendment.”

Lawyer for the accused, Elisabet Massi Fritz said she and her client –who has never been identified – would discuss whether to request a review of the decision to drop the case.

“After today’s decision my client needs time to process everything that has happened over these nine years in order to be able to move on with her life.”

A spokesman for Assange’s legal team said: “From the outset of Sweden’s preliminary investigation, Julian Assange’s expressed concern has been that waiting in the wings was a United States extradition request that would be unstoppable from Sweden – and result in his spending the rest of his life in a US prison.

“Now that the US does seek Mr Assange’s extradition to stand trial on unprecedented charges for journalistic work, it continues to be a matter of extreme regret that this reality has never been properly acknowledged and that the process in Sweden – with which Mr Assange has always expressed his willingness to engage and indeed did so – became so exceptionally politicised itself.”

-with AAP